HIV-1 and AIDS have been categorized as a pandemic, affecting all parts of the world. Gaining insight into the mechanisms by which the virus undergoes its replication cycle in humans can yield important information leading to drug therapy and an overall informative picture on how to treat the virus in infected patients. This project aims to investigate the effect of a viral protein, integrase (IN), on a step in the viral life cycle, uncoating. Upon fusion and entry into a cell, the viral core is released into the cytoplasm where the core must uncoat or release the capsid (CA) protein for subsequent steps to occur, including reverse transcription of viral RNA into cDNA for IN to integrate into the host chromosome. Currently uncoating is a step that remains poorly understood, although CA mutations have been investigated and CA stability has been shown to be crucial for infectivity. The specific relevance of IN in this step has not been addressed. Our lab has characterized the importance of IN on reverse transcription by mutational analysis. One mutation, C130S, contains a cysteine to serine substitution at position 130 of IN. This virus has been shown to be non-infectious, yielding no reverse transcription products, although other steps were normal and reverse transcriptase (RT) was present and functional. This suggested that the defect must be either at or prior to reverse transcription, which we hypothesize is at uncoating. This project will examine three viruses, including wildtype, NL-C130S, and NL-?IN, which contains unexpressed IN. Our aims include: determine the defects of IN mutations on uncoating, how these defects influence morphology and protein composition of cores, and if the underlying mechanism includes a direct or indirect interaction between IN and CA. Our preliminary results indicate that the C130S substitution or lack of IN cause an increase in CA disassembly. We will examine core morphology by electron microscopy and examine protein composition using mass spectrometry and 1D and 2D gel analysis. We will examine a possible interaction between IN and CA by co-immunoprecipitation. The results of this project will undoubtedly give insights to the uncoating step of the viral life cycle, which thus far has remained elusive. Information about IN and how it can affect many different steps of the viral life cycle will also be important and can subsequently be applied to drug therapy. This project will examine the effects of HIV-1 integrase, a viral protein, on the uncoating step of the life cyle. We will also determine any interaction between integrase and capsid, a viral protein known to be important for uncoating. Understanding more about HIV-1 will provide useful information for possible drug therapy.